presumably nowadays we would only aim at stars with a planet with an atmosphere we might at least suspect to be influenced by biology (i.e. contains some gas th

presumably nowadays we would only aim at stars with a planet with an atmosphere we might at least suspect to be influenced by biology (i.e. contains some gas that couldn't be formed and maintained by known geological processes). so maybe aliens would see oxygen in our atmosphere and aim at us - but you'd still have to get the timing right: we might have been burning witches the last time one message came by and next time we might be in the midst of some other social disturbance.